1. Field of the Invention
The present invention relates to a lamination apparatus and a lamination method for a ceramic green sheet and more particularly, the present invention relates to a lamination apparatus and a method of laminating a ceramic green sheet cut piece having a predetermined size which is formed by punching a long ceramic green sheet.
2. Description of the Related Art
For production of laminated ceramic electronic components, a process of laminating plural ceramic green sheets is carried out. In many cases, at least two kinds of ceramic green sheets are laminated in a lamination process. For example, for production of a laminated ceramic capacitor, ceramic green sheets having conductor films formed thereon, which function as internal electrodes for producing electrostatic capacitances, and ceramic green sheets having no conductor films formed thereon, which constitute outer layers, are laminated.
For example, Japanese Unexamined Patent Application Publication Nos. 2002-151350 (Patent Document 1) and 2003-17365 (Patent Document 2) disclose lamination apparatuses suitable for lamination of two kinds of ceramic green sheets as described above.
The lamination apparatus described in Patent Document 1 is formed so that two kinds of ceramic green sheets, i.e., a first ceramic green sheet and a second ceramic green sheet are processed. The lamination apparatus contains a lamination station in which ceramic green sheet cut pieces having a predetermined size formed by punching predetermined areas of the first and second ceramic green sheets are laminated, and first and second punching stations in which the first and second ceramic green sheets are punched, respectively. The first and second punching stations are arranged in opposition to each other via the lamination station.
Moreover, the lamination apparatus contains a punching head for cutting the first and second long ceramic green sheets so as to form cutting lines enclosing predetermined areas of the first and second ceramic green sheets, the punching head being movable to convey the cut pieces from the first or second punching station to the lamination station while holding the formed ceramic green sheet cut pieces.
Patent Document 1 describes the structure in which two punching heads are provided as the above-described punching head. The first punching head can be moved between the first punching station and the lamination station. The second punching head can be moved between the second punching station and the lamination station. The first and second punching heads can be simultaneously moved by rotation of one ball screw. Thereby, while one of the punching heads conducts the punching operation in one punching station, the other punching head can carry out the lamination operation of a ceramic green sheet cut piece in the lamination station. Thus, the cycle time for the lamination process can be reduced.
According to the lamination apparatus described in Patent Document 2, two kinds of ceramic green sheets are processed. One of the two kinds of ceramic green sheets is a long ceramic green sheet, and the other, which is not long, is a card-shaped ceramic green sheet.
Moreover, in the lamination apparatus described in Patent Document 1, only one punching head is provided, which is different from the lamination apparatus described in Patent Document 1. This punching head punches a long ceramic green sheet or a card-shaped ceramic green sheet to form a ceramic green sheet cut piece having a predetermined size in the working station. Also, the punching head has a function to laminate the punched ceramic green sheet cut piece. The long ceramic green sheet and the card-shaped ceramic green sheet are conveyed from their opposite positions into the above-described working station for the punching head.
However, the lamination apparatuses described in patent Documents 1 and 2 have the following problems to be solved.
That is, in the lamination apparatus described in Patent Document 1, the first and second punching stations are arranged in opposition to each other via the lamination station. Thus, the ball screw for driving the punching head must have a length such that the screw can extend at least from the first punching head to the second punching head. Thus, the ball screw must be long, so that the inertial moment of the mechanism for causing the movement of the punching head becomes large. The punching head is unsuitable for high speed movement. Thus, the reduction of the cycle time has a limit.
Moreover, in the lamination apparatus described in Patent Document 1, the cost of the punching head is relatively high. Thus, when two punching heads are provided, the cost of the whole lamination apparatus becomes high.
In the case where the ceramic green sheet cut pieces formed by punching the first long ceramic green sheet, and the ceramic green sheet cut pieces formed by punching the second long ceramic green sheet are alternately laminated one by one, for example, the lamination process can be efficiently carried out, since the two punching heads are provided.
However, in the case where the ceramic green sheet cut pieces formed by punching only one kind of the long ceramic green sheets are laminated in succession many times, i.e., in the case where fifty ceramic green sheet cut pieces formed by punching the first ceramic green sheet are laminated, and thereafter, fifty ceramic green sheet cut pieces formed by punching the second ceramic green sheet are laminated, only one punching head is required during this particular time period. Therefore, the constitution having two punching heads is not necessarily suitable for the above-described use.
For example, for production of laminated ceramic capacitors, ceramic green sheet cut pieces formed by punching a long ceramic green sheet having no conductor film formed thereon are laminated in succession a plurality of times, and thereafter, ceramic green sheet cut pieces formed by punching a long ceramic green sheet having a conductor film formed thereon are laminated in succession a plurality of times. Thus, the constitution having two punching heads is not necessarily effective for a highly efficient lamination process.
On the other hand, the lamination apparatus described in Patent Document 2 is provided with only one punching head, and moreover, the punching head is used for lamination of ceramic green sheet cut pieces thereon. Thus, the problems which the lamination apparatus described in Patent Document 1 encounters, i.e., a limit in reduction of the cycle time and the relatively high cost of the whole lamination apparatus can be solved.
However, one of the ceramic green sheets which are processed with the lamination apparatus described in Patent Document 2 must be a card-type. Accordingly, with this lamination apparatus, two kinds of long ceramic green sheets can not be processed.
To carry out the punching operation with one punching head in one working station, as conducted with the lamination apparatus described in Patent Document 2, while two kinds of long ceramic green sheets are processed as conducted with the lamination apparatus described in Patent Document 1, a mechanism is required by which two kinds of long ceramic green sheets can be selectively supplied to one working station, without interfering with each other. However, it has been difficult to realize this mechanism.